American farmers’ move toward growing more corn for ethanol production has been one of the factors cited for rapidly rising food costs. The negative publicity over the ethanol strategy has put a cloud over the biofuels market.

But General Motors isn’t giving up on the prospect put forth by some reports that American growers and other renewable sources could provide one-third of the nation’s fuel needs by 2050. It held a conference call for reporters last week on which executives of various companies developing ethanol-production technologies — some of which GM has invested in — made their case that materials such as “genetically optimized” grasses and trees and municipal waste can be used to produce cleaner-burning, sustainable sources of fuel that would allow the U.S. to achieve that one-third goal (and, of course, keep GM cars running).

C-Net’s report on the conference call , posted Tuesday, mainly focuses on GM’s arguments for continued development of technologies that would be to its benefit. But there’s good information about what some entrepreneurs are attempting in their efforts to carve out a profitable niche in the search for renewable fuel sources.